Continuous lehr for the heat treatment of glass-based materials



United States Patent [72] inventors Mikhail Ivanovich Kozrnin, MashirApp]. No. Filed Patented Assignee Priority I van Fedotovich Bezbozhny,Vasily Semenovich, Olomsky, and

Veniamin Matveevich, Konstantinovka Donetskoi Obluti, U.S.S.R. 720,816

April 12, 1968 Nov. 17, 1970 Ordena Trudovogo Krasnogo Znameni ZcvodAvtoltekltf,

Konstantinovlta Donetskoiobilsti, U.S.S.R. April 14, 1967 1,144,461 and1,144,462

CONTINUOUS LEIIRFOR THE HEAT TREATMENT OF GLASS-BASED MATERIALS PrimaryExaminer-John J. Camby A rtorney- Waters, Roditi, Schwartz and NissenABSTRACT: A iehr having a heating-chamber below which are combinationchambers on which is superposed a hearth grating. Direct heating devicesare connected to the comcmmsJDnwin Figs bustion chambers and to theupper part of the heating US. Cl. 263/6; chamber through which extends aconveyor. The combustion 65/350 chambers are subdivided by alongitudinal partition.

I I L 1 i 3 2 2. 21 i2 2 1 1 2 2 2 2 6 j I l I \29 7 CONTINUOUS LEHR-ORTHE HEAT TREATMENT or GLASS-BASEDMATERIALS The present inventionrelates to lehrs for heat-treating and more particularly for' effectingcrystallization of glass-based materials.

The lehrs, known in the prior art, are used for annealing glass, theprocess being employed to remove stresses, set up in glass, by slowlycooling it within the range of temperatures .from 610-590"C. to420-370C. and by subsequent intenpart is direct-fired or heated byelectric heaters situated under the roof, the products of combustionbeing removed from the chamber and underhearth ducts through flue ducts.

Owing to their temperature conditions, conventional lehrs are unsuitablefor production of crystallized glass materials since it has been foundthat the process of crystallization requires the material, heated in thecourse of formation, to be slowly cooled down to 680720C. to insure thebeginning of nucleation; soaked at this temperature for a period of timesufficient for complete nucleation; then heated to a temperature of900980C. at which time a gradual precipitation and growth of crystalstake place around the nuclei; subsequently annealed at 480C. and,finally, a cooled down to l-70C. Only in such a manner can structuraltransformations in the glass-based material be accomplished.

An the object of this invention is to provide a continuous lehr with animproved method of heating its heating chamber to insure the temperatureconditions required for crystallization of glass-based materials.

Described in the present invention is a continuous lehr'for the heattreatment of glass-based materials with a conveying device whichtransports the material through the heating chamber of the lehr, thisheating chamber being direct-fired in its upper and lower parts, andconnected to flue ducts. According to a feature of the invention forheating the lower part of the heating chamber, a hearth grating isprovided below the conveying device to form combustion chambers underit, the combustion products entering from these combustion chambers intothe heating chamber via the hearth grating.

In the preferred embodiment of the present invention, cross partitionswith apertures for the conveying device are provided in the, heatingchamber of thelehr, the latter being thus subdivided by the partitionsinto several working chambers interconnected through the apertures.

For a more uniform heating of the lower part of the heating chamber, thecombustion chambers, under the hearth grating are longitudinallysubdivided into several ducts, the preferred number of such ducts beingtwo.

An advantageof the present invention is that it makes it possible todevelop, by simple'means, the desired temperature conditions for theupper and lower parts of the heating chamber as well as to achieve auniform heatingthroughout the material to be crystallized.

Another advantage of the invention is the possibility of maintaining andcontrolling the temperature conditions along the whole length of eachworking compartment as required for the crystallization process of theglass material.

The invention will become more fully apparent from the followingdescription of one embodiment which is given with reference to theaccompanying drawings, in which:

FIG. 1 is a schematic representation of a continuous lehr according tothe invention, shown in a longitudinal section;

FIG. 2 is the head portion of the lehr on enlarged'scale; and

FIG. 3 is an enlarged stepped section through line ABCD of the lehr,shown in FIG. 2.

- The description of theinvention and of the mode ofoperation will bemadefor'the sheet material. t

The proposed continuous lehr for the heat treatment of glass-basedmaterialshas a direct-fired heating chamber I (FIGS. 1 and 3) defined bylongitudinal sidewalls 2, roof 3 and hearth grating 4, enclosed in ametal framework 5 which carries and binds together the brickwork of thelehr.

The heating chamber 1 is direct-fired and ports and II are provided inthe sidewalls 2 for this purpose. The parts arearranged in a staggeredpattern in their corresponding rows. lnspirator-type gas burners 12connected to manifold 13 of a combustible gas supply'are mounted at theentry of the ports 10 and 1]. The ports 11 discharge intocombustionchambers 14 formed under the hearth grating 4 through which the productsof combustion are delivered into the heating chamber 1 via holes 15 ofthe grating.

Along the length of the heating chamber 1, the combustion chambers 14are-separated by cross or transverse partitions 16 (FIGS. 1 and 2) whilein the longitudinal direction these chambers are subdivided bypartitions 17 into two parallel ducts 14a and 14b as shown in FIG. 3.Between the partitions 16 of two adjacent combustion chambers 14vertical ducts 19 are provided, closed by slide dampers l8 andconnecting the working space of the heating chamber 1 to a horizontalunderhearth duct 20 whose middle portion enters flue duct 21 (FIG. 1).From the upper part of the heating chamber 1, the

products of combustion areremoved through vertical ducts 23 provided inthe roof 3 of the heating chamberand closed by slide dampers 22 (FIG.3). These ducts are in communication. with a horizontal overroof duct 24covered by a vault 25 which bears against the framework 5 of the lehrapart from the sidewalls 2. The overroof duct 24 is connected throughtwo flue ducts 26 and '27, to smoke exhausters (not shown) arranged atthe head and tail portions of the lehr.

In order to control and maintain the prescribed temperature conditionsalong the entire length of the heating chamber 1, the latter may besubdivided into several working compartments la, lb, lc(FIG. l) by meansof cross partitions 2 8 with apertures 29 to let the material pass alongthe conveying device 9 and to connect the working compartments with eachother.

Visual observations of the heat treatment of material can beaccomplished through peepholes 30 (FIG. 2) disposed in the.

side walls 2 of the lehr along the entire length of the heating chamber1.

The general principle of operation of the lehr is given below.

Glass materiaL-formed into a strip-31 (FIG. 3), enters the heatingchamber 1 on the conveying device 9 through the aperture 8 in-t'he endwall 6, and is heat treated in accordance number of flamesente't'ing'the heating chamber 1 from the combustion chambers 14 viaopenings'ls in the hearth grating 4. The central portion of the strip,the width of which is equal to that of the partition 17, is heated lessintensively than its. side portions, which results in an equalization oftemperature in the lateral direction of the strip 31, warpage in thelatter being thus avoided.

The temperature conditions in the lehr are controlled by means ofthermocouples (not shown) mounted in the heating chamber 1 and thecombustion chambers 14. The gas atmosphe're within the lehr iscontrolled by means of pressure indicators (not shown) and is adjustedby means of the slide dampers l8 and 22.

The rate of travel of the strip in the heating chamber '1 is adjustedby'changing the speed of the drive of the conveying device 9. Whenemerging from the lehr at its end wall 7, the

case of processing a crystalline glass strip of crystalline glassmaterial is cut into sheets of desired size.

We claim: 1. A continuous le'hr for the heat treatment of a glass-basedmaterial comprising: means providing a heating chamber having upper andlower parts, means for heating the heating chamber in its upper andlower parts respectively by direct-firing; a conveying device fortransporting said material,

disposed in said heating chamber; flue ducts connected to said heatingchamber; a hearth grating disposed in said heating chamber below saidconveying device; means providing combustion chambers to which saidmeans for heating the lower part of the heating chamber is connected,said combustion chambers being covered from above by said hearthgrating, the products of combustion being directed from said combustionchambers through said hearth grating, cross partitions, the heatingchamber being subdivided into a plurality of working chambers by saidcross partitions spaced longitudinally therein, said chambers beinginterconnected through apertures provided in said cross partitionsthrough which extends the conveying device, and longitudinal partitions,the combustion chambers being subdivided below the hearth grating bysaid longitudinal partitions into at least two ducts.

2. A lehr as claimed in claim 1, wherein the second said means providesrows of ports opening into the upper part of the heating chamber andinto the combustion chambers respectively, the ports in one row beingstaggered relative to the ports in the other row.

3. A lehr as claimed in claim 1, comprising a vault covering the heatingchamber, means above the vault providing a horizontal duct extendingalong said heating chamber and connected by selected of said flue ductsto the latter, and slide dampers between the horizontal duct and heatingchamber.

4. A lehr as claimed in claim 3 comprising cross partitions separatingthe combustion chambers. means providing vertical ducts between thelatter said cross partitions coupling adjacent combustion chambers, andslide dampers in said vertical ducts.

